McLarnon J G, Sawyer D, Michikawa M, Kim S U
Department of Pharmacology and Therapeutics, University of British Columbia, Vancouver, Canada.
Neurosci Lett. 1992 Sep 14;144(1-2):185-8. doi: 10.1016/0304-3940(92)90746-t.
A calcium-dependent potassium channel K(Ca) has been isolated in mouse motoneurons. With physiological concentrations of potassium across inside-out patches, a 100 pS K(Ca) channel was activated when the bath solution of Ca2+ was in excess of 1 microM. Introduction of the drug tedisamil, a blocker of repolarizing potassium channels in cardiac cells, at concentrations in the range 0.2-10 microM, caused a dose-dependent decrease in the mean open times for K(Ca). The drug action was consistent with open channel block of K(Ca) with an onward (blocking) rate constant of 6 x 10(7) M-1 s-1. Tedisamil, at concentrations of 1 microM and 5 microM, also blocked the K(Ca) channel when applied to outside-out patches with a similar potency as found with internal application. A large conductance K(Ca) channel in hippocampal neurons is also blocked by a number of putative Class III antiarrhythmic drugs, including tedisamil; thus, these agents may have utility in the characterization of the properties of K(Ca) channels in various cells.
